The invention relates to an intake device, particularly for an internal combustion engine, with a duct section that is provided with noise supressing openings.
Adding openings, particularly bores, is described for instance in DE 1642857. According to this document, the air intake of an air filter housing is provided with a series of bores. To limit the number of bores for production reasons the bores are made in a size large enough to obtain the desired acoustic effect. The bores create short circuits between the tube volume and the environment on the other side of the tube wall. This suppresses or reduces the formation of stationary waves inside the tube and thus dampens the intake noise.
The environment of the tube is normally the engine compartment in which additional engine components are installed. The short circuit between the engine compartment and the interior of the tube, however, causes the pulsation of the intake air to induce vibrations in other components inside the engine compartment. As a result, additional vibration dampening measures may be necessary. Furthermore, hot air from the engine compartment may be sucked in through the bores, which decreases the performance of the internal combustion engine. Moreover, providing the bores in the tube connection involves additional production costs and reduces the economic efficiency of the component. These costs can be kept within limits only by providing a small number of bores.
A fabric hose, which has some air permeability with respect to the environment, could be provided as the duct section. These components have optimal acoustic properties, but they are expensive to produce. In addition, their connection to the intake device involves additional production and assembly costs.
The object of the invention is to create a duct section, particularly for the intake system of internal combustion engines, which has optimal noise dampening properties.
Another object of the invention is to provide a noise damping air intake duct section which is economical to produce.
It is also an object of the invention to provide an air intake duct section with little or not tendency to cause vibrations in adjacent components within the engine compartment.
These and other objects are achieved in accordance with the present invention by providing an air intake device for an internal combustion engine for installation in an engine compartment in which other components of the internal combustion engine are arranged, in which the air intake device comprises a duct section for guiding intake air, and the duct section is provided with a plurality of openings that open into the engine compartment arranged in at least one row extending axially along the duct, and the openings each have a cross sectional area of less than 7 mm2.
The intake device according to the invention comprises a duct section with a series of openings. These openings have a cross section of less than 7 mm2. Compared to the prior art, a larger number of openings can therefore be provided in the duct section, while the total cross section of all the openings combined remains the same or is even smaller. This makes it possible substantially eliminate, or at least to minimize, the vibration inducing influences on components adjacent to the duct section due to pulsation effects in the air intake.
According to one advantageous embodiment of the inventive concept, the openings are configured as round holes. They can then be produced in the form of bores in the wall of the duct section. If the duct section is made of plastic, a greater number of bores may be provided therein while still satisfying economic considerations. Advantageously, the bores have a diameter of about 1.5 mm. It has been shown that rows of bores with a 1.5 mm diameter result in an even greater degree of noise attenuation afforded by the duct section within the problematic frequency range of 100-300 Hertz than would be possible with a fabric hose of the same dimensions as the duct section provided with the bores.
According to one advantageous embodiment of the invention, the duct section is comprised of at least one molded part, especially a part made of a synthetic resin material (i.e., plastic). In this case, the openings may be created by appropriately configuring the mold. As a result, no additional production step to make the openings is required. In this variant, the cross section of the openings does not have to be round. Here, too, it is advantageous if the openings each have a cross sectional area corresponding to bores of 1.5 mm in diameter.
A further embodiment of the invention provides that the openings be formed in the parting seam between two molded parts. The molded parts can then be assembled and joined together by a snap connection. Leakage in the parting seam between the castings can be tolerated. In fact, leakage can further improve intake pipe acoustics and can be used deliberately for this purpose. Arranging the openings in the parting seam of the housing sections has the advantage of requiring only minor modifications in the shape of the housing mold in the edge area. It is even possible to make such modifications in the mold at a later time, for instance if it turns out that the acoustics of an intake system that is almost ready for mass production could be further improved.
From an acoustics point of view, it is particularly advantageous to arrange the openings in one or more rows extending in the direction of air flow through the tube, i.e., axially along the tube. This makes it possible to effectively reduce the formation of standing waves in the attenuating duct section over a larger frequency range. Noise damping is thus facilitated over a greater frequency spectrum.
According to another embodiment of the invention, the duct section can be provided with a cross section that increases in flow direction to enhance the air intake into the duct section. This diffuser-type configuration enhances the air intake into the tube section. This is due to the recovery of speed energy from the pressure loss that occurs at the input of the duct section.
According to another advantageous embodiment of the invention, the cross sectional area of the duct section can be variable. The cross section is changed by a control element, which forms a portion of the wall of the duct section. The openings may be formed both in the stationary parts of the wall and in the control element. The control element may be configured for different cross-sectional shapes. It is feasible, for instance, to vary the angle of the opening of the diffuser. Another possibility is to provide a constant cross-sectional area of the duct section over the length of the control element. This cross-sectional area can then be varied by actuating the control element.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or in the drawings, and the individual features each may be implemented in embodiments of the invention either individually or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.